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                [Usaco2017 Jan]Subsequence Reversal                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><div>Farmer John is arranging his NN cows in a line to take a photo (1&le;N&le;50). The height of the iith co</div>
<div>w in sequence is a(i), and Farmer John thinks it would make for an aesthetically pleasing photo if t</div>
<div>he cow lineup has a large increasing subsequence of cows by height.To recall, a subsequence is a sub</div>
<div>set a(i1),a(i2),&hellip;,a(ik)) of elements from the cow sequence, found at some series of indices i1&lt;i2&lt;</div>
<div>&hellip;&lt;ik, We say the subsequence is increasing if a(i1)&le;a(i2)&le;&hellip;&le;a(ik).FJ would like there to be a l</div>
<div>ong increasing subsequence within his ordering of the cows. In order to ensure this, he allows himse</div>
<div>lf initially to choose any subsequence and reverse its elements.</div>
<div></div>
<div>For example, if we had the list</div>
<div></div>
<div>1 6 2 3 4 3 5 3 4</div>
<div>We can reverse the chosen elements</div>
<div></div>
<div>1 6 2 3 4 3 5 3 4</div>
<div>&nbsp; ^ &nbsp; &nbsp; &nbsp; &nbsp; ^ ^ ^</div>
<div>to get</div>
<div></div>
<div>1 4 2 3 4 3 3 5 6</div>
<div>&nbsp; ^ &nbsp; &nbsp; &nbsp; &nbsp; ^ ^ ^</div>
<div>Observe how the subsequence being reversed ends up using the same indices as it initially occupied,&nbsp;</div>
<div>leaving the other elements unchanged.Please find the maximum possible length of an increasing subseq</div>
<div>uence, given that you can choose to reverse an arbitrary subsequence once.</div>
<div></div>
<p></p></p><hr/><h3>输入格式</h3><p><div>The first line of input contains N. The remaining N lines contain a(1)&hellip;a(N),</div>
<div>each an integer in the range 1&hellip;50.</div>
<div></div>
<p></p></p><hr/><h3>输出格式</h3><p><div>Output the number of elements that can possibly form a longest increasing subsequence&nbsp;</div>
<div>after reversing the contents of at most one subsequence.</div>
<div></div>
<p></p></p><hr/><h3>样例输入</h3><pre>9
1
2
3
9
5
6
8
7
4</pre><hr/><h3>样例输出</h3><pre>9</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>Platinum</p>
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